1. Technical Field to which the Invention Belongs
The present invention relates to an air bag device designed so that an air bag thereof is deployed into an occupant compartment of a vehicle by a gas generated by an inflator upon collision of the vehicle to restrain an occupant.
2. Description of Related Art
When an air bag is deployed into a vehicle compartment by a gas generated by an inflator upon collision of a vehicle, the air bag having a smaller volume at an initial stage of the deployment is expanded quickly, while the air bag having larger volume at a late stage of the deployment is expanded slowly. In addition, the air bag breaks a fragile portion of a lid in the course of the expansion to deploy into the vehicle compartment, and for this reason the air bag may expand suddenly into the vehicle compartment the moment it breaks the lid, in some cases.
Therefore, when the distance between an occupant and the air bag device is small, the following problem may be encountered: the air bag expanded at a high speed at the initial stage of the deployment may interfere with the occupant, thereby making it difficult to restrain the occupant softly. Therefore, it is a conventional practice to elaborate the manner in which the air bag is folded, so that the air bag is expanded essentially upwards at the initial stage of the deployment, thereby avoiding the interference with an occupant disposed in the rear of the air bag.
In the above conventional method, however, the direction of expansion of the air bag is not stabilized due to delicate differences in precisely how the air bag is folded, and it is difficult to reliably avoid the early interference of the air bag with the occupant.
The present invention has been accomplished with the above circumstance in view, and it is an object of the present invention to ensure that the air bag expanded at a high speed at the initial stage of the deployment does not unduly interfere with an occupant or a child seat.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided an air bag device for a vehicle, comprising: a folded-up air bag accommodated in a module cover of a steering wheel; a peripheral edge of an opening in the air bag being fixed to a retainer supporting an inflator so that when the air bag is expanded by a gas generated by the inflator, the air bag is deployed into an occupant compartment of the vehicle through an opening in a lid provided on the module cover; and
a band-shaped deployment-limiting sheet disposed between the folded-up air bag and an inner surface of the module cover, and which is longer than a length of an inner periphery of the module cover in a longitudinal direction of the vehicle;
the folded-up air bag being covered from a rear side of the vehicle to a front side of the vehicle by the deployment-limiting sheet.
With the above arrangement, the folded-up air bag is covered from the rear side of the vehicle to the front side of the vehicle by the deployment-limiting sheet disposed between the folded-up air bag and the inner surface of the module cover. Therefore, the air bag deployed at the initial stage can be inhibited from being expanded rearwards of the vehicle by the deployment-limiting sheet, thereby reliably avoiding the early interference of the air bag with an occupant. Particularly, the deployment-limiting sheet is longer than the length of the inner periphery of the module cover in the longitudinal direction of the vehicle body and hence, it is possible to reliably inhibit the air bag at the initial state of the deployment from being expanded rearwards of the vehicle body.
According to a second aspect and feature of the present invention, there is provided an air bag device for a vehicle, comprising: a folded-up air bag accommodated in a retainer disposed within a dash board of the vehicle; a peripheral edge of an opening in the air bag being fixed to a retainer so that when the air bag is expanded by a gas generated by an inflator supported on the retainer, the air bag is deployed into an occupant compartment of the vehicle through an opening in a lid provided on the dash board, the folded-up air bag being covered from a rear side of the vehicle to a front side of the vehicle by a deployment-limiting sheet disposed between the folded-up air bag and an inner surface of the lid, and which is longer than a reference length; the reference length being as long as an arc of a circle which has a center immediately above a first reference point at a rear end of the lid, passes through said first reference point and which is tangent at a second reference point to a front windshield of the vehicle, the arc extending on the rear side of the vehicle between the first and second reference points.
With the above arrangement, the folded-up air bag is covered from the rear side of the vehicle to the front side of the vehicle by the deployment-limiting sheet disposed between the folded-up air bag and the inner surface of the lid. Therefore, the air bag deployed at the initial stage can be inhibited from being expanded rearwards of the vehicle by the deployment-limiting sheet, thereby reliably avoiding the early interference of the air bag with an occupant. Particularly, the deployment-limiting sheet is longer than the length of the arc of the circle which has its center immediately above the first reference point at the rear end of the lid, passes through the first reference point, and which is tangent at the second reference pointy to the front glass, the arc extending on the rear side of the vehicle body between the first and second reference points. Therefore, it is possible to reliably inhibit the air bag at the initial stage of the deployment from being expanded rearwards of the vehicle body.